Educational demonstrating device



3 Sheets-Sheet 1 W. BOPF April 28, 1931.

EDUCAT I ONAL DEMONSTRATING DEVI CE Filed sept. 7, 192e April 28, 1931. w. BOPP 1,802,331

EDUCATIONAL DEMONSTRATING DEVICE Filed Sept. 7, 1926 3 Sheets-Sheet 2 April 28, 1931. w, BOPF EDUCATIONAL DEMONSTRATING DEVICE Filed Sept. 7, 1926 3 Sheets-Sheet 3 S S s Patented Apr. 28, 1931 UNITED srArss Artur cruce WILLIAI BAPF, 0F WAUSAU, WISCONSIN; AMELIA BOIPIT EXECUTRIX 0Fy THE ESTATE OF SAID VWIIlli'IAlVE BOPF, DECEASED' Y EDUCATIOIr-'L DEMSNSTRATING DEVICE Application filed september 7', 192e.

VMy invention relates in general to educational demonstrating devices, but is more particularly concerned with astronomical ydemonstrating devices that show the movements of the earth and the moon with respect to the sun. e

'l lam aware of'many and various kinds of educational demonstrating devices of this nature, but to my knowledge none of the ex- 10 isting devices Asucceed inV demonstrating all the major movements of the earth and moon with respect to the'lsun, that cause the seasons, and the eclipses of the sun and of the moon in a simple and easily apprehendable manner.

Y The main object of invention is the production of a simple and inexpensive mechanical device for demonstrating the maj or movements of the earth and moon with respect to the sun more completely and more clearly than has heretofore been possible with any existing mechanical demonstrating device.

The construction and operation of my new and improved device I shall fully describe with reference to the accompanying drawings comprising Figs. 1-5, inclusive.

Fig. l is a front view of part of my device, certain elements thereof being shown in section for better illustration.

Fig. 2 is a plan view of a section on the line 2 2' of same part of the device as shown in Fig. 1, with certain parts removed for better illustration.

Fig. 3 is a Idiagram illustrating the grooves or guiding tracks in the base of the device.

Fig. 4 is a left end view of the part of the device shown in Fig. 1, omitting certain parts for the sake of clarity.

Fig. 5 is a top view of the part of the device shown in Fig.y 4.

lt is to be understood, of course, that the relative sizes of the elements representing the earth, moon, and sun, and the relative distances between these elements do not correspond to the relative sizes and distancesof the heavenly bodies they represent-these sizes. and distances of the representing elements vhaving been chosen with the intention of making the device of a convenient size and Serial No. 133,973.

yet so as to clearly and impressivelyillus-1 i trate ythe movements of the heavenly bodies and the phenomena produced by these movements.V

The device, in a general way, comprises the following elements: A stationary standardis centrally mounted on a! base and supports a small electric light bulb which represents the sun. A rotating carriage carries a small sphere to represent the earth, a. smaller spherey to represent the moon, and the gear mechanism for giving the earth and the moon motion with respect to the sun. The rotating carriage is associated with one of the spokes of a large rotary driving wheel' which is also mounted onV the base with the stationary element representing the sun as its center. By imparting rotative motion to this driving Wheel, the carriage carrying the earth and moon is made to rotate about the sun. B means of a gear mechanism carried by the carriage, the earth is made-.to revolve about its own supporting axis simultaneous with its motion about the sun, making about 864 revolutions about its axis for one revolution about `the sun. Its axis is tilted about 23 degrees to the vertical and by a special arrangement Vis made to point alwaysl in one direction (towards the north). By means of another gear mechanism on the carriage and in operative yan association with the first gear mechanism,`the

moon is made to rotate about the earth, making aboutl revolutions about the earth for one revolution of the earth about the sun,this rotative motion taking place 1n a plane which! makes an angle of about l0 degrees with the plane of rotation of the earth about the sun, and which shifts in such a way that a line normal to this plane transcribes a cone with the earth as the. apex point, the time `for one transcription being about 18 times that for one revolution of theearth about the sun* It is evident from the above description to those having a knowledge of astronomy that the bodies which represent the `earth and moon are made to perform all the maj or com- Y ponent movements with respect to the sun that are actually performed by the heavenly bodies in the universe.

I shall now proceed to describe the me'- chanical construction of my device in detail: The device, its stationary and rotating parts rests upon the base 2, preferable made of Wood, either solid, or built up of veneer sheets, the latter being more desirable in that the probabilities of warping are thereby eliminated. n the center of the base 2 the point Z), Fig. 3) the round wooden axle 3 is securely fastened in any suitable manner, such as with glue, or wood-screws passing through the base 2 and screwing into the axle 3. About two-third of the upper portion of the axle is turned down to a smaller size than its larger diameter. This turned down portion and the horizontal surface adjacent thereto are fitted with the metal sleeve 4 and flat metal ring 4 forming suitable bearing surfaces.

The master driving wheel, comprising the rim 5, spokes 5', and the hub 5 is rotatably mounted over the metal sleeve 4', resting on the `metal ring 4. The master driving .wheel is shown as having eight spokes, having T- shaped cross-section as indicated in the conventional manner at 1Q. One of the spokes has an enlarged portion 6 near the end. Through the center of this enlarged portion '6' a hole is bored perpendicularly, forming a. suitable bearing for the hollow shaft 23, to be described later. Teeth are cut on the bottom o' the outer edge of the rim 5, these teeth meshing with the teeth of the driving pinion 19.

The driving pinion 19 is securely fastened to the driving shaft 18 by means of the lock screw screwed through the hub of the pinion 19 and pressing against the shaft- 18. The shaft 18 is supported in the bearing 'member 20, held in proper operative relation to the master driving wheel by means of the collar 20. A hand crank (not shown) may be fastened to the end of the shaft 18 by which rotative motion may be imparted to the shaft, or more preferably, another wheel. may be fastened on the outer end, geared or belted to the shaft of a` small electric motor. The bearing member 2() for su gporting the shaft 18 is fas- -tened to the lower base 2 by means of wood screws 21, and to the upper base 16 to be described later) by means of wood screws 21.

As mentioned above, the hollow shaft 23 passes through the hole bored through the enlarged portion 6 of one spoke 5. The shaft 22 passes through the hollow of this shaft, and threads into the supporting base 16 of the guide plate 16 and is securely fastened in position by means of the lock nut 17, shown clearly in Fig. 1. The guide plate 1" being preferably made. of metal, is rectangular in shape to facilitate its manufacture.

The metal guides 14 and 14 are rotatably fastened to the underside of the guide plateby means of the Hat head screws 13 and 13 equal `istances to either side of the center of the 'guide plate (the center `point of the shaft 22) and in a straight line therewith. A cross section of these metal guides is shown in Fig. 1, and the plan view of guide 14 is partially shown in Fig. Q. These guides are curved so that they may slide freely in the circular tracks 15 and 15 cut into the base 2. These tracks are lined with metal U-shaped lining held in place by means of the screws 63 and 63- l "1 The respective positions of these tracks is diagrammatically shown in Fig. 3, which reference is now made. In Fig. 3, the point b is the center of the base 2, or the center of the axle 3 upon which the lnaster driving wheel is rotatively positioned, and is the center of the dotted circle fr representing the circle transcribed by the center of the guide plate 16. The point a is the center ofthe circle representingthe'track 15l "for the=guide 14, and the point"c is the center of the circle representing the track 15 for the lguide 14. The points a, 1) and c are on a 4straight line, and spaced-equal distances apart.

Considering the apparatus as far asfhas been described, it is evident that ifthemaster driving wheel be rotated, motion being iniparted'thereto by turning the crank or driving themotor fastened or geared tothe shaft 18, the guide'plate V16 isrotated aboutthe center of the axle 3, but by reason of theguides i 14 and 14 which foliow in their 'respective tracks, the guide plate 16 itself is maintained pointing in one direction, i. e., any imaginary line drawn on theguide plate-always remains parallel to itsoriginalposition. In Fig. 3 the` guide plate 16 .1s shown dotted) in two different position-s e and f. t -is evident that as the guide plate 16 makes one complete revolution about the center of t-heaxle r3, the guide 14 makes one complete revolution about its supporting screw 13, and the guide -14 makes one complete revolution about its supporting screw 13. lItis 'further evident therefore that the guides 14 and 14 while lthey should be sufficiently long'so that there is no danger of their not -followin g in their-respective tracks attne points where thetracks cross each other, neither must interfere withfthefrotation of the other about its center point. The reason -for impartingsuch portion to the guide plate and the shaftQQ supported thereby will vbecome obvious from later descriptions.

Returning now to the description of .the construction of the'device, a top board com-k prising the inner' section 10 andthe outer-section 10', is mounted over the base 2. covering the apparatus thus far described. The top board is shown in Figs. 1 and 4, but is removed in Fig. 2 for the vsake of better illustration of the operating mechanism. The inner section 10is circular in shape rof a diameter slightly smallerthan the diameter of thecircle transcribed bythe shaft Q3 in its rotation about the center point b of the aXle 3 to give the shaft 23 comfortable clearance. This inner section is mounted on, and

secured to, the aXle 3Vby means of three or This outer section is supported on the sup-V ports such as 20, three or more of which may kmore screws (only one of which is shown) which pass through the rim of the central circular supporting fixture 6, through the top board section 10, and into the axle 3.

The outer section 10 has an inside hole of a diameter slightly larger than the diameter of the circle transcribed by the shaft 23 in its rotation about the center point b of the aXle 3, again to give comfortable clearance.

y shown) for supplying current tothe bulb 64 pass through the hollow support 8, and through the hole 8 in the top board 10,aXle 3, and base 2. f

The inner section 10 aords ka means for supporting the gear rim 11, the rim 11 being secured to the underside of the toprboard section 10 by means of screws such as screw 24 evenly spaced at frequent intervals. To the hollow shaft 23, which encloses the lower party of the inner shaft 22, the pinion 25 is secured,

held in position by means of the screw 26. The teeth of the pinion engage thoseof the gear rim 11. Thus when rotative motion is imparted to the master drive wheel, the inner shaft 22 is caused to rotate about the center point b, rotation about its own axis being' prevented by means ofthe guide plate 16 and guides 14 and 14. The outer shaft obviously rotates about the center point Z2 but also undergoes an axialrotation by reason of the pinion 25 engaging the teeth of the rim 11. The purpose for giving the outer shaft 25 this motion will becomeobvious fromy later descriptions. Y

The hollow shaft 25 has an enlarged flat portion on its bottom end, which rests and rotates on top of the boss 16. The top of the boss 16 is smoothed oil' to form a good bearing surface. On the upper end of the shaft 23 the gear wheel 28 is mounted and fastened by means of the screw 28 threaded into the hub 27. Gear teeth are also `cut into the upper end of the hub 27 which meshV with the teeth of the gear of the gear train 'to be described presently. The arm'32 ofthe goose-neck member is pivoted to the hub 27 by means of the small pin 11 passing through two projections 27 (only one being shown) and the end of the member 32-the end of the member 32 being` between the projections 27. In operation, the goose-neck supportv rotates with thegear wheel 28 and also moves through a small angle about the pin 11 (to be described further presently).

Some distance above the end of the shaft 23, the circular supporting plate 49 is securely fastened to the shaft 22 by means of the set screw threaded through the'hub 49. FromV this supporting plate 49 the shafts 69, 52, 39, and 35 arev suspended, being held in their proper positions by means of the hub 67 and collar 67 collars 51 and 51', 50 and and 46 and 36, respectively, the collarsy being fastened to the shaft-s by means of suitable set screws. To the bottom end of the shaft 35, the gear combination comprising gear 45, pinion 33, and hub 34, is secured by means of a set screw threaded through the hub 34. To the bottom end of the shaftk 39, the gear combination comprising gear 37, pinion 38, and hub 40, is secured `by means of a set screw threaded through the hub 40. To the bottom end of the shaft 52, the gear 41 is secured byy means of the set screw threaded through its hub 43. To the lowerend of the shaft 69 the pinion 42 is fastened by means of the set screw threaded through its hub 42. The pinion 68 is integral with the hub 67 fastened to the upper end of shaft 69. The positions of the shafts are such'that`V i gear 45 meshes with pinion 44; gear 37 meshes J with pinion 33'; gear 41 meshes with pinion 38; and pinion 42 meshes with gear 41. Y The pinion 68 fastened to the kupper end of the shaft 69 engages the teeth of the orbit control wheel 47. Y

The orbit control wheel 47 rests on its side on the supporting plate 49 and rotates about the center shaft 22. The bottom side of the Vhub and the rim of this wheel 47 are madeV long enough to give ample clearancespace for the ends of the shafts 52, 39, and 35 and for the collars 51,r 50, and 46 holding these shafts, respectively. The upper side of the rim 'is cut on a slant and forms the track upon which the smallwheel rolls.` The plane of this track makes an angle of about 10 degrees with a horizontal plane. The wheel 65 is held in position in the forkof the arm 32 ofthe goose-neck member by means of the small pin.Y

VThe small sphere 61, which represents the moon is suitably fastened on the upper end of the rod 62 which is held rigid in the arm 32 of the goose-neck member.

A short distance above the hub of the. wheel 47, the shaft 22 bends downward making an angle of about 23 degrees with the horizonltal. Some distance above this) bend, the

$58, t'he\ ear wheel .56 .is 'rigidly fastened on the Sheff 59iby meansof the screwi' screwed into vits :lnib. A sphere 60, with the continents fand oceans indicated, `having a diameter about four times `-.that vof sp'here .6,1 is suitably fastened on 'the upper Lend of the shaft- 59 and :represents 'the world.

Beyond the .enlarged portion through which the shurft 59 passes, another hole is :bored through another enlarged Vportion in fthe shaft 22. 'Jlh'rough =this hole, the .shaft 311 passes, being held iin position Vby ymeans off thecollars `555 and 55,each securely fas- .timetl to fthe shaft vby fmeans Vof set screws. The tgear wheel 53 fis rigidly fastened on Athe upper end of the shaft 3l by means of the lset screw athrea ded through :the hub 54. The relative kpositions Vof the shafts 59 and 3'1 is such ythat :the gear ywheels 56 and 53 mesh. 'Qn :the lower-end of the shaft 31 the pinion `:29u15 rigidly `fastened by `means of the lock muts- :amd 30,1the pinion 29 .meshing with 4the gearfl. Just beyondthe upper enlargement of the shaft Q2, the shaft `makes a Aright angle bend lextending downward and Vnear-its lower end the shaft Q2 4makes another :rightiangle bend. This flast vpart is also enilarged -with1a :hole through :it through vwhich shaft -31 passes, 1aiding in holding :the shaft in :its proper {posit-ion to keep the pinion 29 in mesh'with the gear 28.

Ello operate :the Edevicc, the ycrank (not shown) atithe endof `.the vshaft '18 is turned .by shand, or zthefelectric motor geared to the shaft is'operated. The master driving-wheel rotates and drives the carriage aboutitsacen- .ter of rotation in a counter clockwise fdirection. Thus .the body 60 representing the -earth .and sphere 6l :representing the moon is rotated about the central stationary light 64 .representing :the sun. Simultaneously with its rotation about `the sun the earthfalso rotates, also ina counter clockwise direction on its axis by reason Iof the gear-train 56and 153, Aand 29 and 28', the gear 2S being yfastened to the ehollow shaft Q3 which is given axial rotation by virtue of the fpinion fastened `t0 it engaging the toothed .-rim 11. Furthermore the .body 6l representing the moon at the same time rotates in a counter clock-wise direction about the 'body 60 representing `the earth by reason of its being supported on the gooseaicck member which Vis lhinged to the hub of gear'QS `by means of pin 11.l The .orbit Vof the .moon .about the earth is inclined with respect to theorbit of .theearth about the sun and is governed by ,the orbit control wheel 47, the roller 65 rolling on the inclined track-way 48 of this wheel. Furthermore the position of the orbit of the ,moon shifts with respect Vto 'the orbit ofthe earth so that a linenormal to the plane of the orbit ofthe moon transcribes a cone, this beingcontrolled by thergear train supported bythe plate i9 .which slowly rotutes the orbit control wheel in a clock-wise direction. The gear ratios between the various gears are such that the earth revolves on its axis 364 times in making one revolution about the sun. The moon rotates 13 times around the earth while the earth makes one revolution about the sun, and one cycle of the shift of the orbit of the moon takes place each eighteen revolutions of the earth about the sun; i. e. the orbit control `wheel makes one revolution for every eighteen revolutions of the earth about the sun.

Having described my invention, its construction and operation, what I claim is new and desire to have protected by Letters Patent is set forth in the appended claim:

1. In an astronomical demonstrating device, a body representing the sun, a second body representing the earth, means .for rotating said second body about said first body, means controlled by said first means for revolving said second body about a diametrical axis as said second body is rotated about said first body, a base for supporting said first body, a carriage for supporting said second body and means for maintaining said carriage always pointing in the same direction, said last means including .two curved endless non-concentric tracks in said base intersecting at two points and guides, one for each track, fastened to said carriage and adapted to slide in the track, each guide being long enough to reach over cach intersection of the two tracks.

2. In an astronomical. demonstrating device, a first, a second, and a third body representing the sun, earth, and the moon, rcspectively, means for simultaneously imparting rotary motion to the second body about the first body, revolutionary motion to the second body about a. diametrical axis, rotary motion to the third body about the second body in a plane which makes an angle with the plane of rotation of the second body about the first body, means controlled by said first Ameans for changing the position of the pla-ne of rotation of the third body about the' second body with respect to the plane of rotation of the second body about the first body, and means for maintaining the axis of said second body always pointing in one direction, said means comprising a base having curved endless non concentric tracks therein,-and a carriage for supporting said second body having guides fastened thereto adaptedto slide in said tracks.

3. An astronomical demonstrating device comprising ya base, a support centrally mounted on said base, a second base mounted on said support, a body representing vthe sun mounted on said second base, a gear sccured to said second base, a carriage vcomprising a table, a supporting shaft, and a bed plate, curved endless non-concentric tracks in said first hase, guides rotatably ii fastened-to said bed plate and curved toit into said tracks, av master drive wheel for revolving said carriage about the sun, a sleeve rotatable on said shaft, a plnlon se-k cured to said'sleeve and engaging said gear, forcausing said sleeve to rotate on said shaft as the carriage is revolving about the sun, asecond gear beveled on one face resting on said table and rotatable about said shaft, a'

- porting member pivoted to said sleeve, a second 'body representing the moon mounted on said supportingfmember, a roller fastened to said supporting member and adapted to roll on the beveled face of said beveled gear, a Y

second shaft rotatably mounted on said supporting shaft, a third body representing the earth mounted onV said second shaft, a fourth gear secured to said second shaft, and a second gear train supported byl said supporting shaft, the first gear of said second train engaging saidthird gear and the last gear ofsaid second-train engaging said fourth gear,'for causing the earth t0 revolve on its axis as said carriageis revolved about `the sun. v

4. An astronomical demonstrating device comprising a base having curved endless nonconcentric tracks therein, a carriage comprising a table, a supporting shaft, and a bed plate, guides rotatably fastened to said bed plate and curved to-it into said tracks, a body representing the sun, means for revolving said kcarriage about said body, a sleevek rotatable on said shaft, means controlled yby said first means forrotating saidsleeve on said shaft as said carriage4 is revolved about the sun, a second body representingthe earth rotatablymounted on said supporting shaft, and means controlled by said sleevefor rotating said second-body on its Yaxis and for rotating said third body'about said second body as said second body is revolved about said rst body. y n' Y y5.`An astronomical demonstrating device comprising a base hav-ingl curved endless non concentric tracks therein, a carriage coInprisV ing a supporting shaft anda bed plate, guides rotatably'fastenedto said bedl plate and curved to fitV into 'said tracks, a body representing the sun, means for revolving said carriage about said body, said carriage being maintained pointing in a fixed direction by reason of' saidguides following said tracks, a second bodyrotatably mounted on said supporting shaft, a thirdV body representing the moon, and means controlled by said I'irst means .for rotating said ythird body about said first body ina plane with respect to the earth which makes an acute angle withy the plane of revolution of said second body about said `first body, and means controlled by said first means for causing the plane of rotation of said third body about said second body to constantly shift with respect to the plane of revolution of said second bodyk about said first. y

6. In an` astronomical demonstrating device, a first, a second, and a third body representing the sun,.the earth, and the moon respectively, a base for supporting the first body, a carriage for supporting the second and the third body, means for simultaneously imparting revolutionary motion to the second body about the first, revolutionary mo-y tion to the third body about the second, and

rotary motion to the second body abouta diametrical axis, and means for *maintainingy the axis of revolution of said second body always pointing in the same direction, said last` means including two curved endless non-concentric tracks intersecting at two pointsfinsaid base, and guidesfor said tracks fastened to said carriage and adapted to slide insaid tracks, each guide being long enough to reach over` each intersection of the two tracks.

7. In an astronomical demonstrating kdevice, a lirst, a second, anda third body repre-V senting, the sun, the earth, and the moon, respectively, a support upon which said second body is rotatably mounted, a sleeve member embracing said support, means for ro tating saidsleeve about said support, gear means carried by said support for transmitting rotary motion from said sleeve to said second body, an arm for supporting said third body pivoted to said sleeve member, a gear having a beveled face, rotatably carried on said support for determining the :plane of rotation of said arm, gear means for transmitting rotary motion from said sleeve to said beveled face gear, and-means for revolvy ing said support about said ,first body.v

8. In an astronomical demonstrating device, a first, a second, and a third body repre'- senting, the sun, the earth, and the moon, re

spectively, a support upon which said second body is rotatably mounted, a sleeve member embracing said support, means for, rotating,

said sleeve about said'support, gear means carried by said support for transmitting rotary motion from said sleeve to said second body, an arm for supporting said third body pivotedto said sleeve member,a gear having a beveled face rotatably' carried on said sup-,

port for ,determining the plane of rotation ofsaid arm, gear means for transmitting rotary. motion from said sleeve to said beveled face gear, means for revolving said. support about said first body, and means for preventing said support fromV executing any rotary movement while being revolved about said first body. 1 Y

9. In an astronomical demonstrating de-'y vice, a first, ay second, and a third body, repre- Santing, the sun, the earth, and the moon, respectively, a support upon which said second bod is rotatably mounted, aV gear embracing sai f support, rotating means for rotating saidgear about said support, means for transmitting rotary motion from said gear to said second body, an arm pivoted to saidV gear for supporting said third body, a beveled face member rotatably carried on said: support for-controlling the plane of rotation of said arm, means for transmitting rotary motion from said' gear to said beveled face member, and means for revolving said support about 6, said first body, said rotating means being actuated bythe revolution of said support about said first body.

10; InL an astronomical den'ionstrating deve, a first, a second, and a third body, representing, thesun, the earth, and the moon, respectively, a support upon which said second body is rotatably mounted, a gear embracing said*- support, rotating means for rotatingsaidgear about said support, means for transmitting rotary motion from said gear to said seeondbody, a-n arm' pivotcd tesaid gear for supporting said third body, a beveled face member rotatably carried on said support for determining the plane of rotation of said wrm', means for transmitting rotary motion from said gear tosaid beveled face member, means for revolving said support about said; first body, sar-id rot-atingVV means being ac'- tuated by the revolution of said support about said first body, and means for preventingsaid support from executing any rotary movement while being revolved about said first body. .E Y i 11. In an astronomical demonstrating device, a'first, a second, and athird body repre'- senting the' sun, the earth, Vand the moon', respectively, a support upon which said second' body is rotatably mounted, a gear embracing sa'id support, means for rotating said r, a beveled face gear rotatably carried y said support above said first gear, means for-.transmitting relatively slow rotary motionl from sa'id first gear to saidV beveled face gear, an arm pivoted to the hub otsaid 'rst gear and having guiding engagement the beveled face ofV said beveled face gear, meansr'or transmitting relatively fast rotary motionfromsaid first gear to said sec-V ondbod saidv arm having an extension extending 'elow the plane oi said gear and then upwards to approximately the horizontal pl'alflecontainingy said second body Where said third body is supported thereon, and' means for rot-atingsaid support about said first able support upon which said first body is rotatably mounted, a gear Wheel embracing saidL support and rotatable about the air-is-- concentri'cf tracks therein, a carriage` compris-- ing a table, a supporting sha-ft, and a-'bed plate, guides on said bed plateY adapted to follow 1n said tracks, at least one of' saidguides being rotatably supported and having substantially the curvature ofV the track in- Whichit follows, a body representingv the sun, means for revolving said carriage about said body, al sleeverotatable onsaidi shaft, means controlled by said first means or rotating said sleeveon said shaft as said carriageisrevolyed about the sun, asecond body representing the earth rotatably mounted on said supporting shaft, and` means controlledby said sleeve for rotating said second body on its axis and for rotating said third body about said second body'as saidY second body is revolved about saids first body. i

14'. In an astronomical demonstrating device, a first, asecond, and a third body repre senting the sun, the earth, andv the moon re spectively, a base' for supporting the first body, al carriageI for supporting the second andthe third body,means for simultaneously imparting revolutionary motion tothe second body about the first, revolutionary motion tothe third bod-y about the second, and rotary motion to the second/body about al diametrical axis, and means forrmaintaining the axis of revolution of said second body alwaysV pointing in theV same direction, said last means including at least twoV curved endlessnon-concentric tracks intersecting at twov points in saidy base, and guides for said tracks mounted on said carriage and adapted to slide in said tracks, at least'one of said guides being long enough to reachoverY each intersection' of two tracks.

15. In an astronomical demonstrating device, a rst body representing the sun, a carriage supporting at least one body representing the earth, means for moving said carriage about said iirst body, and means for maintaining said carriage in av position of parallelism with respect to-an initial position as it is moved. about said first body, said last means including at least two curved endless non-concentric'tracks intersecting at two points, and guides mounted onV said carriage and adapted to slide in said track, at least one of said guides being rotatably mounted and long enough to reach over an intersection.

In Witness whereof I hereunto subscribe 5 my name this 4th .day of September, A. D.

WILLIAM S BoPF.

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